Tetrahydrophthalimides, and their production and use as herbicides

ABSTRACT

A compound of the formula: ##STR1## wherein X is a chlorine atom or a bromine atom and R is a C 1  -C 8  alkyl group except isopropyl, which is useful as a herbicide.

The present invention relates to N-(2-fluoro-4-halo-5-substituted phenyl)-3,4,5,6-tetrahydrophthalamide derivatives (hereinafter referred to as "tetrahydrophthalimide(s)"), and their production and use.

The tetrahydrophthalimides are representable by the formula: ##STR2## wherein X is a chlorine atom or a bromine atom and R is a C₁ -C₈ alkyl group, preferably a C₁ -C₅ alkyl group (e.g. methyl, ethyl, n-propyl, n-butyl, isobutyl, sec-butyl) except isopropyl.

It is known that certain kinds of N-phenyltetrahydrophthalimides are effective as herbicides. For instance, the herbicidal use of 2-fluoro-4-chlorophenyltetrahydrophthalimide, 2,4-dichloro-5-isopropoxyphenyltetrahydrophthalimide, etc. is disclosed in U.S. Pat. No. 4,032,326, U.K. Patent Publication No. 2,046,754A, etc. However, their herbicidal effect is still not always satisfactory.

It has now been found that the tetrahydrophthalimides of formula (I) show a strong herbicidal activity against a wide variety of weeds including Gramineae weeds, Cyperaceae weeds and broad-leaved weeds at small doses and do not produce any material phytotoxicity on various agricultural crops. Examples of Gramineae weeds against which the tetrahydrophthalimides (I) show a herbicidal activity are barnyardgrass (Echinochloa crus-galli), green foxtail (Setaria viridis), large crabgrass (Digitaria sanguinalis), Johnsongrass (Sorghum halepense), wild oat (Avena fatua), water foxtail (Alopecurus geniculatus), goosegrass (Eleusine indica), annual bluegrass (Poa annua), bermudagrass (Cynodon dactylon), quackgrass (Agropyron repens), etc. Examples of Cyperaceae weeds are nutsedge sp. (Cyperus sp.), purple nutsedge (Cyperus rotundus), hardstem bulrush (Scirpus juncoides), nutsedge (Cyperus serotinus), water chestnut (Eleocharis kuroguwai), slender spikerush (Eleocharis acicularis), etc. Examples of broad-leaved weeds are tall morningglory (Ipomoea purpurea), velvetleaf (Abutilon theophrasti), sicklepod (Cassia obtusifolia), wild sunflower (Helianthus annus), cocklebur (Xanthium pennsylvanicum), wild mustard (Brassica kaber), common chickweed (Stellaria media), common purslane (Portulaca oleracea), jimsonweed (Datura stramonium), hemp sesbania (Sesbania exaltata), sun spurge (Euphorbia helioscopia), prickly sida (Sida spinosa), common ragweed (Ambrosia artemisifolia), smartweed sp. (Polygonum sp.), redroot pigweed ( Amaranthus retroflexus), bedstraw (Galium aparine), pineappleweed (Matricaria spp.), birdseye speedwell (Veronica persica), wild buckwheat (Polygonum convolvulus), ladysthumb (Polygonum persicaria), beggarticks (Bidens spp.), common lambsquarters (Chenopodium album), black nightshade (Solanum nigrum), bindweed (Calystegia japonica), monochoria (Monochoria vaginalis), American waterwort (Elatine americana), false pimpernel (Lindernia procumbens), toothcup (Rotala indica), arrowhead (Sagittaria pygmaea), etc.

Accordingly, the tetrahydrophthalimides (I) can be used as herbicides applicable for field drops and vegetables as well as paddy rice. They are also useful as herbicides to be employed for orchard, lawn, pasture, tea garden, mulberry field, rubber plantation, forest, etc. applications.

The tetrahydrophthalimides (I) can be produced by various procedures, among which typical examples are shown below.

Procedure A

The tetrahydrophthalimide (I) is obtainable by reacting an aniline of the formula: ##STR3## wherein X and R are each as defined above with 3,4,5,6-tetrahydrophilic anhydride, in the absence or presence of an inert solvent (e.g. benzene, toluene, xylene, 1,4-dioxane, acetic acid, propionic acid) while heating. The reaction is normally accomplished at a temperature of 70° to 200° C. for a period of 0.5 to 5 hours. The molar ratio of the aniline (II) and the tetrahydrophthalic anhydride is preferred to be from 1:1.0 to 1:1.1.

PROCEDURE B

The tetrahydrophthalimide (I) is obtainable by reacting a hydroxyphenyltetrahydrophthalimide of the formula: ##STR4## wherein X is as defined above with a halide of the formula: RY wherein Y is a chlorine atom, a bromine atom or an iodine atom and R is as defined above, usually in an inert solvent (e.g. dimethylformamide, dimethylsulfoxide) in the presence of a base such as an alkali metal carbonate (e.g. potassium carbonate), an alkali metal hydroxide (e.g. potassium hydroxide), an alkali metal hydride (e.g. sodium hydride) or an alkali metal alkoxide (e.g. sodium methoxide, sodium ethoxide). The most preferred base is an alkali metal carbonate. The reaction temperature is normally from 0° to 100° C., preferably from 40° to 90° C. The molar ratio of the hydroxyphenyltetrahydrophthalimide (III) and the halide is preferred to be from 1:1.0 to 1:1.1

The thus produced tetrahydrophthalimide (I) may be, when desired, purified by a per se conventional procedure such as recrystallization or column chromatography.

The aniline (II) as the starting material in Procedure A and the hydroxyphenyltetrahydrophthalimide (III) as the starting material in Procedure B can be produced from a phenol of the formula: ##STR5## wherein X is as defined above according to the following scheme: ##STR6## wherein X and R are each as defined above.

Namely, the aniline (II) may be produced from phenol (IV) by nitrating the same, subjecting the resultant nitrophenol (V) to alkylation, and reducing the resulting alkoxy-nitrobenzene (VI). The hydrophenyltetrahydrophthalimide (III) can be manufactured from the phenol (IV) by nitrating the same, reducing the resultant nitrophenol (V) and reacting the resulting aminophenol (VII) with 3,4,5,6-tetrahydrophthalic anhydride.

Conversion of the phenol (IV) into the nitrophenol (V) may be accomplished by application of a per se conventional nitration procedure to the former. Usually, however, the indirect nitration which consists of the following three steps is favorable in achievement of the selective nitration at the desired position: ##STR7## wherein X is as defined above. Thus, the phenol (IV) is converted into its alkali metal salt by treatment with an aqueous solution of an alkali metal hydroxide (e.g. sodium hydroxide, potassium hydroxide), and the resulting salt is reacted with an alkyl haloformate such as methyl chloroformate in water at a temperature of 0° to 10° C. The thus prepared carbonic ester (VIII) is nitrated with a mixture of conc. sulfuric acid and conc. nitric acid at room temperature. Then, the nitrobenzene (IX) thus obtained is hydrolyzed with an aqueous alkaline solution such as an aqueous sodium hydroxide solution at a temperature of 20° to 120° C. to give the nitrophenol (V).

The alkylation for conversion of the nitrophenol (V) into the alkoxy-nitrobenzene (VI) may be carried out by treatment of the former with an alkali metal carbonate (e.g. potassium carbonate), an alkali metal hydride (e.g. sodium hydride) or an alkali metal alkoxide (e.g. sodium methoxide) and reacting the resultant alkali metal salt with a halide of the formula: RY wherein R and Y are each as defined above in a polar solvent (e.g. water, dimethylformamide, acetonitrile, acetone, dimethylsulfoxide), usually at a temperature of 10° to 200° C., preferably of 30° to 100° C. The use of a phase transfer catalyst such as tetrabutylammonium bromide is favorable for smooth accomplishment of the reaction.

Reduction of the alkoxy-nitrobenzene (VI) to the aniline (II) may be achieved in various procedures. For instance, there may be adopted a per se conventional reduction procedure for converting a nitro group into an amino group wherein a reducing agent such as sodium sulfide or iron powder or catalytic reduction is employed. One of the typical procedures comprises introduction of a 3 molar amount of hydrogen into a reaction system comprising one molar amount of the compound (VI) and a 1/10 to 1/100 molar amount of platinum dioxide at room temperature under atmospheric pressure. Another typical procedure comprises admixing an acetic acid solution containing one molar amount of the compound (VI) with a 5% acetic acid solution containing a 2 to 5 molar amount of iron powder such as reductive iron or electrolytic iron and effecting the reaction at a temperature of 80° to 100° C.

Conversion of the nitrophenol (V) into the aminophenol (VII) may be accomplished by any per se conventional reduction procedure for changing a nitro group to an amino group. Examples of such reduction procedure are catalytic reduction, reduction with iron powder, reduction with sodium sulfide, reduction with sulfurated sodium borohydride, etc. For instance, treatment of one molar amount of the nitrophenol (V) with a 3 molar amount of hydrogen in the presence of a 1/10 to 1/100 molar amount of platinum dioxide in an inert solvent (e.g. ethanol, ethyl acetate) at room temperature under atmospheric pressure affords the aminophenol (VII). Further, for instance, treatment of one molar amount of the nitrophenol (V) with a 2 to 5 molar amount of iron powder such as reductive iron or electrolytic iron in a 5% acetic acid solution or a dilute hydrochloric acid solution at a temperature of 80° to 100° C. for a period of 1 to 5 hours produces the aminophenol (VII).

For production of the hydroxyphenyltetrahydrophthalimide (III) from the aminophenol (VII), the latter is reacted with 3,4,5,6-tetrahydrophthalic anhydride in an inert solvent (e.g. acetic acid) while refluxing for a period of 1 to 6 hours, preferably of 2 to 4 hours.

Still, the phenol (IV) is known (cf. Finger et al.: J.Am.Chem.Soc., 81, 94 (1959)).

Practical and presently preferred embodiments of the production of the objective tetrahydrophthalimide (I) as well as the intermediary compounds including those of the formula: ##STR8## wherein R' is a hydrogen atom, a C₁ -C₈ alkyl group except isopropyl and X is as defined above are illustratively shown below:

EXAMPLE 1

Production of the tetrahydrophthalimide (I: X=Cl; R=n-amyl):

To a solution of N-(4-chloro-2-fluoro-5-hydroxyphenyl)-3,4,5,6-tetrahydrophthalimide (2.95 g) in dimethylformamide (20 ml), there were added anhydrous potassium carbonate (7.6 g) and n-amyl bromide (1.6 g) in this order. The resultant mixture was stirred at 70°-80° C. for 3 hours. Water was added thereto, followed by extraction with ether. The ether layer was washed with water, dried and concentrated. The residue was purified by silica gel chromatography to obtain 0.63 g of N-(4-chloro-2-fluoro-5-n-amyloxyphenyl)-3,4,5,6-tetrahydrophthalimide (Compound No. 7).

M.P., 100.8° C.

NMR δ (ppm): 0.9 (3H, t, like m), 1.5 (4H, m), 1.8 (6H, m), 2.4 (4H, m), 3.9 (2H, t, J=6 Hz), 6.65 (1H, d, J=6 Hz), 7.25 (1H, d, J=10 Hz).

EXAMPLE 2

Production of the tetrahydrophthalimide (I: X=Br; R=CH₃):

4-Bromo-2-fluoro-5-methoxyaniline (1.1 g) and 3,4,5,6-tetrahydrophthalic anhydride (0.8 g) were dissolved in acetic acid (5 ml) and refluxed for 3 hours. The resultant mixture was allowed to cool to room temperature and poured into water, followed by extraction with ether. The ether extract was washed with water, dried over anhydrous sodium sulfate and subjected to filtration. The filtrate was concentrated under reduced pressure and the residue was purified by silica gel chromatography to obtain 0.6 g of N-(4-bromo-2-fluoro-5-methoxyphenyl)-3,4,5,6-tetrahydrophthalimide (Compound No. 12).

M.P., 105°-106° C.

NMR δ (ppm): 1.8 (4H, m), 2.4 (4H, m), 3.8 (3H, s), 6.65 (1H, d, J=6 Hz), 7.38 (1H, d, J=10 Hz).

Examples of the tetrahydrophthalimide (I) produced by either of Procedures (A) and (B) are shown in Table 1.

                  TABLE 1                                                          ______________________________________                                          ##STR9##                                                                        Com-                                                                         pound                                                                          No.                                                                              X          R       Physical property                                         ______________________________________                                         1        Cl      CH.sub.3     M.P. 115.2° C.                            2        Cl      C.sub.2 H.sub.5                                                                             M.P. 90-91° C.                            3        Cl      n-C.sub.3 H.sub.7                                                                           N.sub.D.sup.22 1.5472                            4        Cl      sec-C.sub.4 H.sub.9                                                                         N.sub.D.sup.23.5 1.5512                          5        Cl      iso-C.sub.4 H.sub.9                                                                         M.P. 58-59° C.                            6        Cl      n-C.sub.4 H.sub.9                                                                           M.P. 74-75° C.                            7        Cl      n-C.sub.5 H.sub.11                                                                          M.P. 100.8° C.                            8        Cl      n-C.sub.6 H.sub.13                                                                          M.P. 60-61.6° C.                          9        Cl      n-C.sub.7 H.sub.15                                                                          n.sub.D.sup.25.5 1.5381                          10       Cl      n-C.sub.8 H.sub.17                                                                          n.sub.D.sup.25.5 1.5303                          11       Cl      iso-C.sub.5 H.sub.11                                                                        M.P. 85-87° C.                            12       Br      CH.sub.3     M.P. 105-106° C.                          13       Br      C.sub.2 H.sub.5                                                                             M.P. 110-111° C.                          14       Br      n-C.sub.3 H.sub.7                                                                           M.P. 76-77° C.                            15       Br      sec-C.sub.4 H.sub.9                                                                         M.P. 84.5-85.5° C.                        ______________________________________                                    

EXAMPLE 3

Production of the aniline (II: X=Cl; R=n-C₃ H₇):

A suspension of 4-chloro-2-fluoro-5-n-propoxy-nitrobenzene (13.5 g) and platinum dioxide (0.4 g) in ethanol (300 ml) was subjected to catalytic reduction with hydrogen under room temperature and atmospheric pressure, whereby a designed amount of hydrogen was absorbed. The resultant mixture was filtered to remove insoluble materials, and the filtrate was concentrated. The residue was subjected to purification by silica gel chromatography to obtain 5.6 g of 4-chloro-2-fluoro-5-n-propoxyphenylaniline. n_(D) ²⁴.5 1.5386.

NMR (CDCl₃) δ (ppm): 1.1 (3H, t, J=6 Hz), 1.85 (2H, m), 3.6 (2H, m), 3.9 (2H, t, J=6 Hz), 6.32 (1H, d, J=8 Hz), 6.98 (1H, d, J=10 Hz).

Some examples of the anilines (II) produced in the same manner as above are shown in Table 2.

                  TABLE 2                                                          ______________________________________                                          ##STR10##                                                                           X        R            Physical property                                  ______________________________________                                         Cl         C.sub.2 H.sub.5                                                                             N.sub.D.sup.24.5 1.5503                                Br         C.sub.2 H.sub.5                                                                             n.sub.D.sup.25.0 1.5680                                Cl         n-C.sub.3 H.sub.7                                                                           n.sub.D.sup.24.5 1.5386                                Br         n-C.sub.2 H.sub.7                                                                           n.sub.D.sup.26.0 1.5618                                ______________________________________                                    

EXAMPLE 4

Production of the hydroxyphenyltetrahydrophthalimide (III: X=Cl):

2-Chloro-4-fluoro-5-aminophenol (6.6 g) and 3,4,5,6-tetrahydrophthalic anhydride (6 g) were dissolved in acetic acid (20 ml) and refluxed for 2 hours. The resultant mixture was allowed to cool to room temperature and poured into ice-water, followed by extraction with ether. The ether extract was washed with a saturated sodium hydrogen carbonate solution and water in this order, dried over anhydrous magnesium sulfate and concentrated. The residue was purified by silica gel chromatography to obtain 4.0 g of N-(4-chloro-2-fluoro-5-hydroxyphenyl)-3,4,5,6-tetrahydrophthalimide. M.P., 151° C.

NMR (CDCl₃, D₆ -DMSO) δ (ppm): 1.5-2.0 (4H, m), 2.1-2.6 (4H, m), 6.8 (1H, d, J=6 Hz), 7.15 (1H, d, J=10 Hz).

IR ν_(max) ^(nujol) (cm⁻¹): 3380, 1680.

EXAMPLE 5

Production of the hydroxyphenyltetrahydrophthalimide (III: X=Br):

In the same manner as in Example 4 but using 2-bromo-4-fluoro-5-aminophenol in place of 2-chloro-4-fluoro-5-aminophenol, there was produced N-(4-bromo-2-fluoro-5-hydroxyphenyl)-3,4,5,6-tetrahydrophthalimide.

M.P., 167°-168° C.

NMR (CDCl₃, D₆ -DMSO) δ (ppm): 1.5-2.0 (4H, m), 2.1-2.7 (4H, m), 6.8 (1H, d, J=6 Hz), 7.25 (1H, d, J=10 Hz).

IR ν_(max) ^(nujol) (cm⁻¹): 3380, 1690.

EXAMPLE 6

Production of the alkoxy-nitrobenzene (VI: X=Cl, R=CH₃):

2-Chloro-4-fluoro-5-nitrophenol (9.6 g) and potassium carbonate (3.8 g) were stirred in acetonitrile (50 ml). Methyl iodide (14 g) was added thereto and refluxed for 3 hours. Water was added to the reaction mixture, followed by extraction with ether. The ether extract was washed with water, dried and concentrated. The residue was recrystallized from ethanol to obtain 8.9 g of 4-chloro-2-fluoro-5-methoxynitrobenzene. M.P., 67.5-69.8° C.

NMR (CDCl₃) δ (ppm): 3.8 (3H, s), 7.25 (1H, d, J=10 Hz), 7.48 (1H, d, J=6 Hz).

Some of the alkoxy-nitrobenzenes (VI) produced in the same manner as above are shown in Table 3.

                  TABLE 3                                                          ______________________________________                                          ##STR11##                                                                          X       R                Physical property                                ______________________________________                                         Cl       CH.sub.3         M.P. 67.5-69.8° C.                            Br       CH.sub.3         M.P. 72.2° C.                                 Cl       CH.sub.2 CH.sub.3                                                                               M.P. 47-48° C.                                Br       CH.sub.2 CH.sub.3                                                                               M.P. 46-46.5° C.                              Cl       CH.sub.2 CH.sub.2 CH.sub.3                                                                      M.P. 46-47° C.                                Br       CH.sub.2 CH.sub.2 CH.sub.3                                                                      M.P. 46.8-47.4° C.                            Cl       CH(CH.sub.3)CH.sub.2 CH.sub.3                                                                   M.P. 59.6-60.6° C.                            ______________________________________                                    

EXAMPLE 7

Production of the aminophenol (VII: X=Cl):

A suspension of 2-chloro-4-fluoro-5-nitrophenol (9.17 g) and platinum dioxide (500 mg) in ethanol (120 ml) was subjected to catalytic reduction with hydrogen under room temperature and atmospheric pressure until a designed amount of hydrogen was absorbed. The catalyst was removed by filtration, and the filtrate was concentrated. The residue was extracted with ether, and the ether layer was concentrated to obtain 6.6 g of 3-amino-6-chloro-4-fluorophenol. M.P., 145°-146° C. (decomp.).

NMR (CDCl₃, D₆ -DMSO) δ (ppm): 6.4 (1H, d, J=8 Hz), 6.85 (1H, d, J=11 Hz).

IR ν_(max) ^(nujol) (cm⁻¹): 3400, 3320.

EXAMPLE 8

Production of the aminophenol (VII: X=Br):

In the same manner as above but using 2-bromo-4-fluoro-5-nitrophenol in place of 2-chloro-4-fluoro-5-nitrophenol, there was produced 3-amino-6-bromo-4-fluorophenol.

M.P., 129°-130.5° C. (decomp.).

NMR (CDCl₃, D₆ -DMSO) δ (ppm): 6.57 (1H, d, J=8 Hz), 7.1 (1H, d, J=11 Hz).

IR ν_(max) ^(nujol) (cm⁻¹): 3400, 3320.

EXAMPLE 9

Production of the nitrophenol (V: X=Cl):

2-Chloro-4-fluorophenol (83.4 g) was added to a solution of sodium hydroxide (27.7 g) in water (450 ml), and methyl chloroformate (69.2 g) was dropwise added thereto at a temperature of below 10° C. Precipitated crystals were collected by filtration and washed with water to give methyl (2-chloro-4-fluorophenyl)formate (134.8 g). M.P., 69°-71° C.

Methyl (2-chloro-4-fluorophenyl)formate (134.8 g) obtained above was suspended in conc. sulfuric acid (50 ml). To the suspension, a mixture of conc. sulfuric acid (50 ml) and conc. nitric acid (50 ml) was added at about 30° C., and the mixture was stirred for 1 hour at this temperature. The reaction mixture was poured into ice water, and precipitated crystals were collected and washed with water. Methyl (2-chloro-4-fluoro-5-nitrophenyl)formate (143 g) was thus obtained. M.P., 53°-55° C.

The product obtained as above was combined with sodium hydroxide (27 g) and water (300 ml), and the resultant mixture was refluxed for 4 hours. Precipitated insoluble materials were filtered using a celite, and the filtrate was acidified with conc. hydrochloric acid. Precipitated crystals were filtered and washed with water to obtain 76.3 g of 2-chloro-4-fluoro-5-nitrophenol. M.P. 106°-107° C.

NMR (CDCl₃, D₆ -DMSO) δ (ppm): 7.25 (1H, d, J=10 Hz), 7.64 (1H, d, J=6 Hz).

IR ν_(max) ^(nujol) (cm⁻¹): 3370.

EXAMPLE 10

Production of the nitrophenol (V: X=Br):

2-Bromo-4-fluorophenol (28 g) was added to a solution of sodium hydroxide (7 g) in water (100 ml), and methyl chloroformate was dropwise added thereto at a temperature of below 10° C. Precipitated crystals were collected by filtration and washed with water to give methyl (2-bromo-4-fluorophenyl)formate (41 g). M.P., 80.7° C.

The thus obtained methyl (2-bromo-4-fluorophenyl)formate was suspended in conc. sulfuric acid (13 ml). To the suspension, a mixture of conc. sulfuric acid (13 ml) and conc. nitric acid (13 ml) was added at about 30° C. The mixture was stirred for 30 minutes and poured onto ice. Precipitated crystals were thoroughly washed with water, whereby yellow crystals of methyl (2-bromo-4-fluoro-5-nitrophenyl)formate (38.3 g) were obtained. M.P., 63.5°-64.5° C.

The product thus obtained was refluxed together with sodium hydroxide (6.2 g) and water (100 ml) for 3 hours. Insoluble materials were filtered, and the filtrate was acidified with hydrochloric acid. Precipitated crystals were collected by filtration and washed with water to obtain 25 g of 2-bromo-4-fluoro-5-nitrophenol. M.P., 126°-127° C.

NMR (CDCl₃, D₆ -DMSO) δ (ppm): 7.42 (1H, d, J=10 Hz), 7.65 (1H, d, J=6 Hz).

IR ν_(max) ^(nujol) (cm⁻¹): 3450.

In the practical usage of the tetrahydrophthalimides (I), they may be applied as such or in any preparation form such as wettable powders, emulsifiable concentrates, granules, suspensions or dusts.

In producing such a preparation form, a solid or liquid carrier may be used. As for the solid carrier, there may be exemplified mineral powders (e.g. kaolin, bentonite, montmorillonite, talc, diatomaceous earth, mica, vermiculite, gypsum, calcium carbonate, apatite, synthetic water-containing silicon hydroxide), vegetable powders (e.g. soybean powder, wheat flour, wooden powder, tobacco powder, starch, crystalline cellulose), high molecular weight compounds (e.g. petroleum resin, polyvinyl chloride, dammar gum, ketone resin), alumina, wax and the like.

As for the liquid carrier, ther may be exemplified alcohols (e.g. methanol, ethanol, ethylene glycol, benzyl alcohol), aromatic hydrocarbons (e.g. toluene, benzene, xylene, methylnaphthalene), halogenated hydrocarbons (e.g. chloroform, carbon tetrachloride, monochlorobenzene), ethers (e.g. dioxane, tetrahydrofuran), ketones (e.g. acetone, methylethylketone, cyclohexanone), esters (e.g. ethyl acetate, butyl acetate, ethylene glycol acetate), acid amides (e.g. dimethylformamide), nitriles (e.g. acetonitrile), ether alcohols (e.g. ethylene glycol ethyl ether), water and the like.

A surface active agent used for emulsification, dispersion or spreading may be any of the non-ionic, anionic, cationic and amphoteric type of agents. Examples of the surface active agent include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, oxyethyleneoxypropylene polymers, polyoxyethylene alkyl phosphates, fatty acid salts, alkyl sulfates, alkyl sulfonates, alkylaryl sulfonates, alkyl phosphates, polyoxyethylene alkyl sulfate, quaternary ammonium salts, and the like. But the surface active agent is not of course limited to these compounds. And, if necessary, gelatin, casein, sodium alginate, starch, agar, polyvinyl alcohol ligninsulfonic acid or the like may be used as an auxiliary agent.

In the preparation of a herbicidal composition, the content of the tetrahydrophthalimide (I) may be from 1 to 95% by weight, preferably from 3 to 80% by weight.

The tetrahydrophthalimide (I) of the invention may be used together with other herbicides to improve their activity as herbicides, and in some cases, a synergistic effect can be expected. Further, they may be also applied in combination with insecticides, nematocides, fungicides, plant growth regulators or fertilizers, depending upon the need.

The dosage rate of the tetrahydrophthalimide (I) may vary on their kinds, the sorts of cultivated plants, the modes of application, etc. Generally, however, the dosage rate is from 0.1 to 50 grams, preferably from 0.5 to 30 grams, of the active ingredient per are.

Practical embodiments of the herbicidal composition according to the invention are illustratively shown in the following examples wherein parts and % are by weight.

PREPARATION EXAMPLE 1

Eighty parts of Compound No. 1, 2 or 3, 3 parts of alkylsulfate, 2 parts of ligninsulfonate and 15 parts of water-containing silicon hydroxide are well mixed while being powdered to obtain a wettable powder.

PREPARATION EXAMPLE 2

Ten parts of Compound No. 1, 2 or 5, 3 parts of alkylarylsulfate, 7 parts of polyoxyethylene alkylaryl ether, 60 parts of cyclohexanone and 20 parts of xylene are well mixed while being powdered to obtain an emulsifiable concentrate.

PREPARATION EXAMPLE 3

Five parts of Compound No. 1 or 2, 1 part of water-containing silicon hydroxide, 35 parts of bentonite and 59 parts of kaolin are well mixed while being powdered. The mixture is then kneaded with water, granulated and dried to obtain a granule.

PREPARATION EXAMPLE 4

Three parts of Compound No. 1, 2 or 3, 0.3 part of isopropyl phosphate, 66.7 parts of kaolin and 30 parts of talc are well mixed while being powdered to obtain a dust.

PREPARATION EXAMPLE 5

Twenty parts of Compound No. 10 is mixed with 60 parts of an aqueous solution containing 3% polyoxyethylene sorbitan monolaurate and grained until the particle size of the active ingredient becomes less than 3 microns. Twenty parts of an aqueous solution containing 3% of sodium alginate as a dispersing agent is introduced therein to obtain a suspension.

The application of the tetrahydrophthalimides (I) as herbicides will be illustratively shown in the following Examples wherein the phytotoxicity to cultivated plants and the herbicidal activity on weeds were evaluated as follows: the aerial parts of the test plants were cut off and weighed (fresh weight); the percentage of the fresh weight of the treated plant to that of the untreated plant was calculated with the latter fresh weight taken as 100; and the crop damage and the herbicidal activity were evaluated by the standard given in the table below. The rating values of phytotoxicity, 0 and 1, and those of herbicidal effect, 5 and 4, are generally regarded as satisfactory to protect cultivated plants and control weeds, respectively. The rating values in the paddy field test alone were calculated from the dry weight of the test plants.

    ______________________________________                                                    Fresh weight                                                        Rating     (percentage to untreated plot) (%)                                  value      Crop plant   Weeds                                                  ______________________________________                                         5           0-39        0                                                      4          40-59         1-10                                                  3          60-79        11-20                                                  2          80-89        21-40                                                  1          90-99        41-60                                                  0          100           61-100                                                ______________________________________                                    

The following control compounds were used in the Examples:

    ______________________________________                                         Com-                                                                           pound                                                                          No.   Structure               Remarks                                          ______________________________________                                                ##STR12##              U.S. Pat. No. 4,032,326                            B                                                                                   ##STR13##              U.K. Patent Publn. No. 2046754A                    C                                                                                   ##STR14##              Chloro- nitrofen                                 ______________________________________                                    

TEST EXAMPLE 1

Plastic beakers (diameter, 10 cm; height, 10 cm) were filled with upland field soil, and the seeds of corn, barnyardgrass, wild oat, wild mustard and velvetleaf were separately sown in the beakers and grown for 2 weeks in the greenhouse. A designed amount of the test compound was sprayed to the foliage of the test plants by means of a small hand sprayer. After the spraying, the test plants were further grown for 3 weeks in the greenhouse, and herbicidal activity was examined. The results are shown in Table 4. In this foliar treatment, the test compounds were formulated into an emusifiable concentrate according to Preparation Example 2 and applied at a spray volume of 5 liters per are by dispersing it in water with the addition of a spreading agent.

                  TABLE 4                                                          ______________________________________                                         Dosage                                                                         (weight of          Herbicidal activity                                        Com-  active in-                                                                               Phyto-  Barn-                                                  pound gredient, toxicity                                                                               yard- Wild Wild   Velvet-                              No.   g/are)    Corn    grass oat  mustard                                                                               leaf                                 ______________________________________                                         1     5         1       5     5    5      5                                          1.25      0       1     1    5      5                                    2     5         1       5     5    5      5                                          1.25      0       3     3    5      5                                    3     5         1       5     5    5      5                                          1.25      0       4     4    5      5                                    4     5         1       5     5    5      5                                          1.25      0       1     2    4      5                                    5     5         0       4     4    5      5                                          1.25      0       2     1    3      5                                    6     5         0       4     3    5      5                                          1.25      0       3     1    4      5                                    12    5         1       5     5    5      5                                          1.25      1       2     1    4      5                                    13    5         1       5     5    5      5                                          1.25      0       2     2    5      5                                    14    5         1       5     5    5      5                                          1.25      0       3     3    5      5                                    15    5         1       5     5    5      5                                          1.25      0       2     2    5      5                                    A     5         2       3     1    5      5                                          1.25      1       1     0    3      5                                    B     5         1       2     1    3      5                                          1.25      0       0     0    2      5                                    ______________________________________                                    

TEST EXAMPLE 2

Seeds of corn and broad-leaved weeds such as cocklebur, common purslane and tall morningglory were sown in the field as previously laid up in ridges, each ridge having an upper width of 1 m. At the time when the corn grew up to the 6-leaf stage and the broad-leaved weeds up to 2 to 5-leaf stages, a designed amount of the test compound formulated into an emulsifiable concentrate according to Preparation Example 2 and dispersed in water was sprayed to the foliage of the test plants with three replications over the top by means of a small hand sprayer at a spray volume of 5 liters per are. After cultivation for 3 weeks, herbicidal activity and phytotoxicity were examined. The results are shown in Table 5.

                  TABLE 5                                                          ______________________________________                                               Dosage                                                                         (weight of                                                               Com-  active in-                                                                               Phyto-  Herbicidal activity                                    pound gredient,  toxicity                                                                              Cock-  Common Tall morning-                            No.   g/are)    Corn    lebur  purslane                                                                              glory                                    ______________________________________                                         7     0.63      0       5      5      4                                              0.32      0       4      5      3                                              0.16      0       4      5      2                                        A     1.25      1       4      3      2                                              0.63      0       1      2      2                                        B     1.25      1       4      4      4                                              0.63      1       2      3      3                                        ______________________________________                                    

TEST EXAMPLE 3

Plastic trays (35 cm×25 cm×15 cm) were filled with upland field soil, and the seeds of tall morningglory, velvetleaf and sicklepod and the seeds of corn were sown therein. A designed amount of the test compounds formulated into a wettable powder according to Preparation Example 1 was dispersed in water and applied by spraying at a spray volume of 5 liters per are to the whole surface of the soil. After the spraying, the test plants were placed in a greenhouse and grown for 20 days, and herbicidal activity and phytotoxicity were examined. The results are shown in Table 6.

                  TABLE 6                                                          ______________________________________                                               Dosage                                                                         (weight of                                                               Com-  active in-                                                                               Phyto-   Herbicidal activity                                   pound gredient,  toxicity                                                                               Tall morning-                                                                           Sickle-                                                                              Velvet-                                No.   g/are)    Corn     glory    pod   leaf                                   ______________________________________                                         2     10        0        4        5     5                                            5         0        4        4     5                                      3     10        0        5        5     5                                            5         0        4        4     5                                      4     10        0        5        4     5                                            5         0        4        4     5                                      5     10        0        5        4     5                                            5         0        4        4     5                                      6     10        0        4        4     5                                            5         0        4        4     5                                      A     10        3        0        1     4                                            5         2        0        0     3                                      B     10        0        0        1     3                                            5         0        0        0     1                                      ______________________________________                                    

TEST EXAMPLE 4

Plastic beakers (diameter, 10 cm; height, 10 cm) were filled with upland field soil, and the seeds of corn, cotton and soybean and the seeds of morningglory, velvetleaf, Johnsongrass and green foxtail were separately sown in the beakers. A designed amount of the test compound was sprayed over the top by means of a small hand sprayer. After the spraying, the test plants were grown for 20 days in the greenhouse, and herbicidal activity and phytotoxicity were examined. The results are shown in Table 7. In this pre-emergence treatment, the test compounds were formulated into an emusifiable concentrate according to Preparation Example 2 and applied at a spray volume of 5 liters per are by dispersing it in water with the addition of a spreading agent.

                                      TABLE 7                                      __________________________________________________________________________     Dosage                                                                         (weight of                                                                     active in-              Herbicidal activity                                    Compound                                                                             gredient,                                                                            Phytotoxicity                                                                              Morning-                                               No.   g/are)                                                                               Corn                                                                              Cotton                                                                             Soybean                                                                             glory                                                                               Velvetleaf                                                                           Johnsongrass                                                                          Green foxtail                        __________________________________________________________________________     1     10    2  2   0    5    5     5      5                                          2.5   1  0   0    4    5     5      4                                    2     10    1  0   0    4    5     5      5                                          2.5   0  0   0    4    5     4      4                                    3     10    1  --  --   4    5     5      5                                          2.5   0  --  --   4    5     4      4                                    12    10    1  --  0    5    5     5      5                                          2.5   0  0   0    --   5     5      5                                    13    10    0  1   1    5    5     5      5                                          2.5   0  0   0    --   4     4      4                                    14    10    0  0   1    4    5     4      4                                          2.5   0  0   0    --   4     4      4                                    15    10    0  1   1    5    5     4      4                                          2.5   0  0   0    --   4     4      --                                   A     10    2  --  --   2    5     3      4                                          2.5   0  --  --   1    4     1      1                                    B     20    1  --  --   1    3     2      0                                           5    0  --  --   0    1     1      0                                    __________________________________________________________________________

TEST EXAMPLE 5

Plastic trays (35 cm×25 cm×15 cm) were filled with upland field soil, and the seeds of tall morningglory, velvetleaf, jimsonweed, sicklepod, hemp sesbania, prickly side, Johnsongrass, green foxtail and large crabgrass and the seeds of soybean were sown therein. A designed amount of the test compound formulated into a wettable powder according to Preparation Example 1 and dispersed in water was sprayed over the top by means of a small hand sprayer at a spray volume of 5 liters per are. After the spraying, the test plants were grown in a greenhouse for 20 days, and phytotoxicity and herbicidal activity were examined. The results are shown in Table 8.

                                      TABLE 8                                      __________________________________________________________________________     Dosage                                                                         (weight                                                                        of active       Herbicidal activity                                                  ingre-                                                                              Phyto-                                                                              Tall           Hemp        Green                                                                              Large                           Compound                                                                             dient,                                                                              toxicity                                                                            morning-                                                                            Velvet-                                                                             Jimson-                                                                             ses-                                                                               Prickly                                                                            Sickle-                                                                            fox-                                                                               crab-                                                                              Johnson                     No.   g/are)                                                                              Soybean                                                                             glory                                                                               leaf weed bania                                                                              sida                                                                               pod tail                                                                               grass                                                                              grass                       __________________________________________________________________________      1    9    0    5    5    5    5   5   5   5   5   5                                 3    0    4    5    5    5   5   4   5   5   5                           12    9    0    5    5    5    5   5   5   5   5   5                                 3    0    4    5    5    4   5   4   5   5   5                           A     20   2    1    5    5    5   5   2   5   5   5                                 10   1    0    5    4    3   5   1   5   5   4                           B     20   0    0    5    4    2   4   2   4   4   3                                 10   0    0    4    4    1   3   0   3   3   2                           __________________________________________________________________________

TEST EXAMPLE 6

Wagner's pots (1/5000 are) were filled with paddy field soil containing the seeds of broad-leaved weeds (e.g. monochoria, false pimpernel, toothcup) and the seeds of barnyardgrass and hardstem bulrush, and water was poured therein until the depth of water became 4 cm. Rice seedlings of the 3.5-leaf stage and the tubers of arrowhead were transplanted therein and grown for 2 days in a greenhouse. A designed amount of the test compound formulated in an emulsifiable concentrate according to Preparation Example 2 was applied to the pots by perfusion. Thereafter, the test plants were grown for an additional 3 weeks in the greenhouse, and herbicidal activity and phytotoxicity were examined. The results are shown in Table 9. In this treatment, the emulsifiable concentrate was dispersed in water for application at a perfusion volume of 10 liters per are.

                  TABLE 9                                                          ______________________________________                                         Dosage                                                                         (weight                                                                        of active  Phyto-  Herbicidal activity                                         Com-  ingre-   toxicity                                                                               Barn- Broad-                                            pound dient,   Rice    yard- leaved                                                                               Hardstem                                                                              Arrow-                               No.   g/are)   plant   grass weed  bulrush                                                                               head                                 ______________________________________                                         1     2.5      1       5     5     4      5                                          1.25     1       4     5     --     4                                    A     2.5      1       2     5     3      0                                          1.25     0       1     5     2      0                                    B     2.5      0       3     5     2      0                                          1.25     0       1     5     1      0                                    ______________________________________                                    

TEST EXAMPLE 7

Wagner's pots (1/5000 are) were filled with paddy field soil and water was poured therein to make a flooded condition. Rice seedlings of the 3-leaf stage were transplanted and tubers of slender spikerush and arrowhead and the seeds of barnyardgrass, monochoria and broad-leaved weed were sowed therein and grown for 5 days. When germination occurs, a designed amount of the test compound formulated into an emulsifiable concentrate according to Preparation Example 2 was applied to the pots by dripping. The test plants were grown for further a 3 weeks, and herbicidal activity and phytotoxicity were examined. The results are shown in Table 10. The herbicidal activity was evaluated in figures ranging from 0 to 5. The phytotoxicity to the crop plants was also indicated on the same standard as that of the herbicidal activity.

    ______________________________________                                         Figures   Percentage of growth inhibition (%)                                  ______________________________________                                         0          0-9                                                                 1         10-29                                                                2         30-49                                                                3         50-69                                                                4         70-89                                                                5          90-100                                                              ______________________________________                                    

                                      TABLE 10                                     __________________________________________________________________________     Dosage                                                                         (weight                                                                        of active  Phyto-                                                              ingre-     toxicity                                                                           Herbicidal activity                                             Compound                                                                             dient,                                                                              Rice                                                                               Barnyard-    Broad-leaved                                                                          Slender                                                                             Allow-                                 No.   g/are)                                                                              plant                                                                              grass Monochoria                                                                            weed   spikerush                                                                           head                                   __________________________________________________________________________     7     5    0   5     5      5      5    5                                            2.5  0   5     5      5      5    4                                            1.25 0   4     5      5      4    3                                      8     5    0   5     5      5      5    5                                            2.5  0   5     5      5      4    5                                            1.25 0   4     5      5      4    4                                      9     5    0   5     5      5      4    4                                            2.5  0   4     5      5      4    4                                            1.25 0   4     5      5      3    3                                      10    5    0   5     5      5      4    4                                            2.5  0   4     5      5      3    4                                            1.25 0   3     5      5      3    3                                      11    5    0   5     5      5      5    5                                            2.5  0   5     5      5      4    4                                            1.25 0   4     5      5      4    3                                      A     10   2   4     5      5      4    3                                            5    1   3     5      5      3    3                                            2.5  1   1     4      4      2    2                                      E     10   1   4     5      5      4    3                                            5    0   3     4      5      3    1                                            2.5  0   2     3      4      1    0                                      __________________________________________________________________________ 

What is claimed is:
 1. A compound of the formula: ##STR15## wherein X is a chlorine atom or a bromine atom and R is a C₁ -C₈ alkyl group except isopropyl.
 2. The compound according to claim 1, wherein R is a C₁ -C₅ alkyl group except isopropyl.
 3. The compound according to claim 1, wherein R is a methyl group.
 4. A herbicidal composition which comprises the compound according to claim 1 as an active ingredient and an inert carrier.
 5. A method for controlling weeds which comprises applying as an active ingredient a herbicidally effective amount of the compound of the formula: ##STR16## wherein X is a chlorine atom or a bromine atom and R is a C₁ -C₈ alkyl group except isopropyl. 